Fluorinated compounds have a high potential in numerous fields of application. However, the use of many compounds is limited because of their method of preparation, which is sometimes expensive and/or difficult to implement.
For example, hexafluorobutadiene is used in the etching of electronic components. It is prepared by various processes involving coupling reactions of C2 compounds with fluorine F2. The starting materials are often fluorinated organic compounds containing one or more atoms of another halogen. The preparation of hexafluorobutadiene by coupling of trichloroethylene in the presence of fluorine F2, followed by a series of stages which alternate dehydrochlorination and fluorination by F2, is known in particular from U.S. Pat. No. 8,536,387. This type of reaction tends to generate numerous byproducts which reduces the overall yield of the process.
The preparation of hexafluorobutadiene in four stages: (1) thermal dimerization of 1,2-dichloro-1,2-difluoroethylene to give 1,3,4,4-tetrachloro-1,2,3,4-tetrafluoro-1-butene, (2) chlorination of 1,3,4,4-tetrachloro-1,2,3,4-tetrafluoro-1-butene to give 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane, (3) fluorination of 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane to give 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane, and (4) dechlorination of 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane to give hexafluorobutadiene, is also known from GB 798 407.
Another synthetic route consists in employing reactions for the fluorination of hexachlorobutadiene in the liquid phase. However, these reactions do not make possible the complete fluorination of hexachlorobutadiene to form hexafluorobutadiene. The fluorination of hexachlorobutadiene in the presence of potassium fluoride in order to form a mixture of 2,2-dichloroperfluoropropane and 2-chloro-2-hydroperfluoropropane is known in particular from U.S. Pat. No. 3,287,425.
There thus still exists a need to make possible the preparation of hexafluorobutadiene by selective and affordable reactions.